JP7289103B2 - Thermosetting resin compositions, prepregs, metal-clad laminates, printed wiring boards, resin-coated films and resin-coated metal foils - Google Patents

Description

TECHNICAL FIELD The present disclosure generally relates to thermosetting resin compositions, prepregs, metal clad laminates and printed wiring boards. Specifically, the present disclosure relates to a thermosetting resin composition containing a thermosetting resin and an inorganic filler, a prepreg comprising a semi-cured product of the thermosetting resin composition, and a metal clad comprising a cured product of the prepreg. It relates to laminates and printed wiring boards.

Patent Literature 1 discloses a cured product obtained by curing an epoxy resin composition. This epoxy resin composition contains an epoxy resin and a predetermined polyhydric hydroxy resin curing agent as essential components. The content of naphthol monomers in this polyhydric hydroxy resin is 0.8% by weight or less, and the Gardner color number of a 10% by weight methyl ethyl ketone solution of the polyhydric hydroxy resin is 13 or less.

By the way, after applying a liquid photosensitive resist or pasting a film-like photosensitive resist (dry film) on both sides of a substrate such as a printed wiring board, a desired pattern is formed on each surface by performing double-sided exposure. Forming a cured film having

In the double-sided exposure described above, each surface is irradiated with ultraviolet rays through a photomask. In this case, so-called back burn becomes a problem. In other words, back burn is a phenomenon in which ultraviolet rays irradiated to one side of a substrate pass through the inside of the substrate and expose the photoresist on the other side of the substrate where it is not desired to be exposed. This problem is aggravated with the progress of thinning of substrates in recent years, and it is difficult to solve even if substrates are manufactured using a cured product such as that disclosed in Patent Document 1.

Japanese Patent Application Laid-Open No. 2001-261785

An object of the present disclosure is to provide a thermosetting resin composition, a prepreg, a metal-clad laminate, a printed wiring board, a resin-coated film, and a resin-coated metal foil that can provide a cured product with high UV shielding properties. .

A thermosetting resin composition according to an aspect of the present disclosure is a thermosetting resin composition containing a thermosetting resin and an inorganic filler. The thermosetting resin contains a curing agent. A 3% by mass methyl ethyl ketone solution of the curing agent has a Gardner color number of 15 or more. The content of the curing agent is 10% by mass or more with respect to the total solid content of the thermosetting resin composition.

A prepreg according to an aspect of the present disclosure includes a base material and a semi-cured material of the thermosetting resin composition impregnated in the base material.

A metal-clad laminate according to an aspect of the present disclosure includes an insulating layer formed of a cured prepreg and a metal layer formed on one side or both sides of the insulating layer.

A printed wiring board according to an aspect of the present disclosure includes an insulating layer formed of the cured prepreg, and conductor wiring formed on one side or both sides of the insulating layer.

1 is a schematic cross-sectional view of a prepreg according to one embodiment of the present disclosure; FIG. FIG. 2 is a schematic cross-sectional view of a metal-clad laminate according to one embodiment of the present disclosure. FIG. 3 is a schematic cross-sectional view of a printed wiring board according to one embodiment of the present disclosure. 4A to 4D are schematic cross-sectional views showing each step of the manufacturing method of the printed wiring board of the same. 5A to 5C are schematic cross-sectional views showing each step of the manufacturing method of the coated printed wiring board. 6A is a schematic cross-sectional view of a resin-coated film according to one embodiment of the present disclosure; FIG. FIG. 6B is a schematic cross-sectional view showing another example of the resin-coated film according to one embodiment of the present disclosure. FIG. 7 is a schematic cross-sectional view of a resin-coated metal foil according to an embodiment of the present disclosure;

(1) Outline The thermosetting resin composition according to the present embodiment contains a thermosetting resin and an inorganic filler. A thermosetting resin contains a curing agent. The Gardner color number of a 3% by mass methyl ethyl ketone solution of the curing agent is 15 or more. The content of the curing agent is 10% by mass or more with respect to the total solid content of the thermosetting resin composition.

According to the present embodiment, the curing agent easily absorbs ultraviolet rays, and a predetermined amount of such a curing agent is contained in the thermosetting resin composition, so that a cured product with high ultraviolet shielding properties can be obtained. can.

(2) Details (2.1) Thermosetting resin composition The thermosetting resin composition according to the present embodiment contains a thermosetting resin and an inorganic filler. Thermosetting resins and inorganic fillers are essential ingredients. The thermosetting resin composition may further contain optional components other than the essential components as long as the effects of the essential components are not impaired. Each component of the essential component and the optional component will be described below.

(2.1.1) Thermosetting Resins Thermosetting resins are low-molecular-weight compounds (eg, prepolymers or oligomers) with reactive groups. When the thermosetting resin is heated, a cross-linking reaction (curing reaction) proceeds to form an insoluble and infusible substance (cured material) having a three-dimensional structure.

Specific examples of thermosetting resins include epoxy resins, bismaleimide resins, phenolic resins and cyanate resins.

Specific examples of epoxy resins include triphenylmethane-type epoxy resins, biphenylaralkyl-type epoxy resins, naphthalene-type epoxy resins, phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, and dicyclopentadiene-containing phenol novolak-type epoxy resins. be done. When the thermosetting resin is an epoxy resin, its epoxy equivalent is preferably in the range of 158 g/eq to 275 g/eq, more preferably in the range of 158 g/eq to 235 g/eq. Within this range, the crosslink density is increased, and the glass transition temperature (Tg) of the cured product can be increased. By increasing the Tg, the dimensional stability and heat resistance reliability of the cured product can be improved.

Bismaleimide resins can give cured products with higher heat resistance than epoxy resins.

A thermosetting resin contains a curing agent. In this embodiment, the Gardner color number of a 3% by mass methyl ethyl ketone solution of the curing agent is 15 or more. Here, the Gardner color number can be determined by the Gardner color number test method. The definition of the Gardner color number and the Gardner color number test method conform to JIS K 0071-2.

That is, the Gardner color number is a color number determined by comparing the transmitted colors of the Gardner color number standard solution and the sample. Gardner Color Standards are prepared using potassium hexachloroplatinate(IV), iron(III) chloride, cobalt(II) chloride and hydrochloric acid. The Gardner color number is represented by a number of colors ranging from 1 to 18. As a rule, the color of a sample is represented by a single integer. Exceptionally, if the color of the sample is between two Gardner Color Standards, determine the Gardner Color Number that most closely matches the sample and express it as "lighter" or "darker" than that color number. . Instead of the Gardner Color Standards, standard color glasses with equivalent transmission colors may be used.

The above sample is a 3% by weight solution of the curing agent in methyl ethyl ketone. That is, this sample is prepared by dissolving a curing agent in a solvent, methyl ethyl ketone, so that the concentration of the curing agent, which is a solute, is 3% by mass.

Hereinafter, a curing agent having a Gardner color number of 15 or more in a 3% by mass methyl ethyl ketone solution may be referred to as a first curing agent. A curing agent other than the first curing agent may be referred to as a second curing agent. That is, the Gardner color number of the 3% by mass methyl ethyl ketone solution of the second curing agent is in the range of 1 or more and 14 or less. Unless otherwise specified, the Gardner color number means the Gardner color number of a 3% by mass methyl ethyl ketone solution.

Since the first curing agent has a Gardner color number of 15 or more (the upper limit is 18), when it is contained in the thermosetting resin composition, it can impart high UV shielding properties to the cured product. That is, the first curing agent undergoes a cross-linking reaction to form a cured product, and the portion derived from the first curing agent in this cured product can absorb ultraviolet rays. Although the second curing agent cannot impart a UV shielding property as high as that of the first curing agent to the cured product, it may be used in combination with the first curing agent.

The content of the first curing agent is 10% by mass or more with respect to the total solid content of the thermosetting resin composition. When the content of the first curing agent is 10% by mass or more, a cured product having high ultraviolet shielding properties can be obtained. For example, when an insulating layer is formed of such a cured product, when one surface of the insulating layer is irradiated with ultraviolet rays, the ultraviolet rays are absorbed inside the insulating layer and blocked, and are transmitted from the other surface. is suppressed.

The ultraviolet light has a wavelength range that sensitizes the photosensitive resist. For example, the wavelength of ultraviolet rays is within the range of 350 nm or more and 450 nm or less. If the content of the first curing agent is less than 10% by mass, the UV shielding properties of the cured product will be low. When the insulating layer is formed of such a cured product, when one surface of the insulating layer is irradiated with ultraviolet rays, part of the ultraviolet rays can be absorbed inside the insulating layer, but the remaining ultraviolet rays are absorbed by the other surface. can penetrate through the surface.

In this way, the first curing agent, which absorbs ultraviolet rays more easily than the second curing agent, is contained in the thermosetting resin composition at a content of 10% by mass or more, so that curing with high ultraviolet shielding properties can get things.

Specific examples of the first curing agent include naphthalene-type phenolic resins and novolac-type phenolic resins.

Preferably, the naphthalene-type phenolic resin contains at least one naphthalene ring and at least one benzene ring in one molecule. Naphthalene rings, benzene rings, and naphthalene rings and benzene rings are linked by, for example, a divalent organic group (methylene group ( _--CH.sub.2-- ), etc.). In this naphthalene-type phenolic resin, each naphthalene ring has at least one hydroxy group (--OH) and each benzene ring has at least one hydroxy group (phenolic hydroxy group).

In other words, the naphthalene-type phenol resin preferably contains at least one naphthol skeleton and at least one phenol skeleton in one molecule. A naphthol skeleton is represented, for example, by the following formula (A) or the following formula (C). A naphthol skeleton is a skeleton in which one or more hydrogen atoms in a naphthalene ring are substituted with hydroxy groups. A phenol skeleton is represented by the following formula (B), for example. A phenol skeleton is a skeleton in which one or more hydrogen atoms in a benzene ring are substituted with hydroxy groups.

In formulas (A) and (C), each of R1, R3 and R5 is a hydrogen atom (H), a methyl group (-CH ₃ ), a methoxy group (-OCH ₃ ) or a hydroxy group, and R1, R3 and at least one of R5 is a hydroxy group. In formula (B), each of R2 and R4 is a hydrogen atom, a methyl group or a hydroxy group, and at least one of R2 and R4 is a hydroxy group. One line segment in formula (A) and two line segments in formulas (B) and (C) represent bonds with other structural sites.

Since naphthalene-type phenolic resins contain naphthalene rings, the conjugated system is larger than that of novolac-type phenolic resins containing benzene rings. Therefore, the absorption peak wavelength of the naphthalene-type phenolic resin is located on the longer wavelength side than the absorption peak wavelength of the novolac-type phenolic resin. That is, the naphthalene-type phenolic resin absorbs ultraviolet rays more easily than the novolac-type phenolic resin. Therefore, the first curing agent preferably contains a naphthalene-type phenolic resin.

By including the naphthalene-type phenolic resin in the first curing agent, the Tg of the cured product can be increased. Therefore, the heat resistance and flame resistance of the cured product can be improved. Furthermore, the hygroscopicity and coefficient of thermal expansion of the cured product can be reduced.

Preferably, the naphthalene-type phenolic resin is represented by the following formula (D). This naphthalene-type phenolic resin includes a naphthol skeleton represented by formulas (A) and (C) and a phenol skeleton represented by formula (B).

In formula (D), each of R1, R3 and R5 is a hydrogen atom, a methyl group, a methoxy group or a hydroxy group, and at least one of R1, R3 and R5 is a hydroxy group. In formula (D), each of R2 and R4 is a hydrogen atom, a methyl group or a hydroxy group, and at least one of R2 and R4 is a hydroxy group.

In formula (D), n is an integer of 1-3, and m is an integer of 0-3. In the naphthalene-type phenolic resin represented by formula (D), the arrangement order of the phenol skeleton represented by formula (B) and the naphthol skeleton represented by formula (C) is not particularly limited. That is, in the naphthalene-type phenol resin represented by the formula (D), the phenol skeletons represented by the formula (B) may or may not be continuous, and the phenol skeleton represented by the formula (C) The naphthol skeletons may or may not be continuous. In short, the naphthalene-type phenol resin represented by formula (D) has one naphthol skeleton represented by formula (A), n phenol skeletons represented by formula (B), and formula (C). It suffices if it has m number of represented naphthol skeletons.

Preferably, the naphthalene-type phenolic resin is represented by the following formula (E). This naphthalene-type phenol resin is a specific example of the naphthalene-type phenol resin represented by formula (D).

In formula (E), R1 is a hydrogen atom, a methyl group or a methoxy group. In formula (E), R2 is a hydrogen atom or a methyl group. In formula (E), n is an integer of 1-3, and m is an integer of 0-3.

Furthermore, the naphthalene-type phenolic resin is preferably oxidized. More specifically, the hydroxy group of the naphthalene ring contained in the naphthalene-type phenolic resin is preferably oxidized. When a hydroxy group is oxidized, it becomes an oxo group (=O).

For example, an oxidized naphthalene-type phenolic resin has a naphthoquinone skeleton. The naphthoquinone skeleton includes, for example, a 1,4-naphthoquinone skeleton represented by the following formula (F) and a 1,2-naphthoquinone skeleton represented by the following formula (G).

In Formula (F) and Formula (G), each of R6 and R7 is a hydrogen atom, a methyl group, an ethyl group (--CH ₂ CH ₃ ) or a methoxy group. Note that two line segments in formulas (F) and (G) represent bonds with other structural sites.

Preferably, the oxidized naphthalene-type phenol resin has at least one skeleton of a 1,4-naphthoquinone skeleton represented by formula (F) and a 1,2-naphthoquinone skeleton represented by formula (G). including. The naphthalene-type phenolic resin oxidized in this way can be obtained, for example, by subjecting the naphthalene-type phenolic resin represented by formula (D) or formula (E) to oxidation treatment. As a method of oxidation treatment, for example, (1) a naphthalene-type phenolic resin is placed in a non-sealed container and the container is left to stand or stirred in the presence of air, and (2) a naphthalene-type phenolic resin is placed in a non-sealed container. (3) a method in which the naphthalene-type phenolic resin is confined together with air in a sealed container and left to stand or stirred; The temperature of the oxidation treatment is, for example, within the range of 50° C. or higher and 100° C. or lower. The oxidation treatment time is, for example, within the range of 6 hours or more and 72 hours or less.

Oxidation of the naphthalene-type phenolic resin further shifts the absorption peak wavelength to the longer wavelength side.

The curing agent contained in the thermosetting resin composition is preferably only the first curing agent, but may be both the first curing agent and the second curing agent.

The thermosetting resin preferably further contains a reactive flame retardant. A reactive flame retardant forms a crosslinked structure when the thermosetting resin composition is cured. Specific examples of reactive flame retardants include phosphorus-modified phenolic resins, tetrabromobisphenol A and tribromophenol. Since the reactive flame retardant does not exist in isolation in the cured product and participates in the formation of a crosslinked structure, it is possible to improve the flame resistance (flame retardancy) of the cured product while suppressing bleed out.

The reactive flame retardant is preferably a reactive phosphorus-based flame retardant. A halogen-free thermosetting resin composition can be obtained by using a reactive phosphorus-based flame retardant instead of halogen. Specific examples of reactive phosphorus-based flame retardants include phosphorus-modified phenolic resins. When the reactive phosphorus-based flame retardant is a phosphorus-modified phenolic resin, its hydroxyl equivalent is preferably in the range of 350 g/eq to 600 g/eq, more preferably in the range of 373 g/eq to 550 g/eq. is.

(2.1.2) Inorganic filler The inorganic filler can contribute to the improvement of the dimensional stability of the cured product of the thermosetting resin composition. Specific examples of inorganic fillers include fused silica, aluminum hydroxide, magnesium hydroxide, E-glass powder, aluminum oxide, magnesium oxide, titanium dioxide, potassium titanate, calcium silicate, calcium carbonate, clay and talc. Among these, fused silica and aluminum hydroxide are preferred.

Since fused silica is spherical, moldability can be ensured even if the content in the thermosetting resin composition is large to some extent. Furthermore, fused silica can contribute to lowering the thermal expansion coefficient of the cured product, improving laser workability, improving drilling workability, stabilizing dimensions, and the like. However, if the fused silica is excessive, the moldability of the thermosetting resin composition may deteriorate. Further, since fused silica is harder than aluminum hydroxide, if the content is excessive, the laser workability and drill workability of the cured product may deteriorate.

Aluminum hydroxide can contribute to improving the flame resistance of the cured product. However, if aluminum hydroxide is excessive, there is a risk that the moldability of the thermosetting resin composition will be reduced and the cured product will be more likely to absorb moisture than when the same amount of fused silica is used. .

Fused silica and aluminum hydroxide may be used in combination, or only fused silica may be used. In such a case, the ratio of fused silica to the total mass of fused silica and aluminum hydroxide is preferably in the range of 50% by mass or more and 100% by mass or less. Such optimum amounts provide the benefits of each of fused silica and aluminum hydroxide. That is, it is possible to achieve a low coefficient of thermal expansion, flame resistance, laser workability, and drill workability of the cured product.

The average particle size of the inorganic filler is preferably in the range of 0.5 µm or more and 5 µm or less. As used herein, "average particle size" means a particle size (d50) at an integrated value of 50% in a particle size distribution measured by a laser diffraction/scattering method.

The content of the inorganic filler is preferably 200 parts by mass or less with respect to 100 parts by mass of the thermosetting resin. When the content of the inorganic filler is 200 parts by mass or less, the moldability of the thermosetting resin composition can be improved. Furthermore, generation of voids in the cured product of the thermosetting resin composition can be suppressed. The content of the inorganic filler is preferably 50 parts by mass or more with respect to 100 parts by mass of the thermosetting resin.

(2.1.3) Optional Components Specific examples of optional components include core-shell rubbers, acrylic resins, additive flame retardants, and curing accelerators. These components are described in order below.

The thermosetting resin composition preferably further contains core-shell rubber, acrylic resin, or both core-shell rubber and acrylic resin.

First, the core-shell rubber will be explained. Core-shell rubber is an aggregate of rubber particles having a core-shell structure. A rubber particle is formed of a core and a shell. At least one of the core and shell has elasticity. By including such a core-shell rubber in the thermosetting resin composition, the impact resistance, thermal shock resistance, laser processability, and drill processability of the cured product can be enhanced. Preferably, the core-shell rubber contains silicone in at least one of the core and shell. This can further enhance the thermal shock resistance. In other words, the impact resistance can be enhanced even at lower temperatures than when silicone is not included.

The core is particulate rubber. Rubbers may be copolymers or homopolymers. Specific examples of copolymers include silicone/acrylic copolymers. Specific examples of homopolymers include crosslinked acrylic polymers. A crosslinked acrylic polymer is a homopolymer of an acrylic monomer and has a three-dimensional crosslinked structure.

A shell exists on the surface of the core. The shell consists of multiple graft chains. One end of each graft chain is bonded to the surface of the core to form a fixed end, and the other end is a free end. A graft chain may be a copolymer or a homopolymer. Specific examples of copolymers include acrylonitrile/styrene copolymers. A specific example of the homopolymer is polymethyl methacrylate.

The average particle size of the core-shell rubber is preferably in the range of 0.1 µm or more and 0.7 µm or less. When the core-shell rubber has an average particle size of 0.1 μm or more, the impact resistance of the cured product can be further enhanced. When the average particle size of the core-shell rubber is 0.7 μm or less, the core-shell rubber can be easily dispersed uniformly in the thermosetting resin composition, and as a result, it can be easily dispersed uniformly in the cured product.

The content of the core-shell rubber is preferably in the range of 10 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the thermosetting resin. When the content of the core-shell rubber is within this range, it is possible to improve the impact resistance, drill workability, and laser workability of the cured product while appropriately maintaining the moldability of the thermosetting resin composition. .

Next, the acrylic resin will be explained. The acrylic resin preferably has a structure represented by at least the following formulas (2) and (3) among the following formulas (1), (2) and (3). An acrylic resin having such a structure will be described below, but the present invention is not limited to this acrylic resin.

x in formula (1), y in formula (2), and z in formula (3) satisfy the following relational expressions. x: y: z (molar fraction) = 0: 0.95: 0.05 to 0.2: 0.6: 0.2 (where x + y + z ≤ 1, 0 ≤ x ≤ 0.2, 0.6 ≤ y ≤ 0.95, 0.05 ≤ z ≤ 0.2). In formula (2), R1 is a hydrogen atom or a methyl group, and R2 is a hydrogen atom, an alkyl group, a glycidyl group and an epoxidized alkyl group, at least one of a glycidyl group and an epoxidized alkyl group. including. In formula (3), R3 is a hydrogen atom or a methyl group, R4 is a phenyl group (-Ph), -COOCH ₂ Ph or -COO(CH ₂ ) ₂ Ph.

The main chain of the acrylic resin has a structure represented by at least formula (2) and formula (3) out of formula (1), formula (2) and formula (3).

When the main chain of the acrylic resin has the structures represented by formulas (1), (2) and (3), the arrangement of the structures represented by formulas (1), (2) and (3) The order is not particularly limited. In this case, in the main chain of the acrylic resin, the structures represented by formula (1) may or may not be continuous, and the structures represented by formula (2) may be continuous. may be discontinuous, and the structures represented by formula (3) may be discontinuous or discontinuous.

Also when the main chain of the acrylic resin has the structures represented by the formulas (2) and (3), the arrangement order of the structures represented by the formulas (2) and (3) is not particularly limited. In this case, in the main chain of the acrylic resin, the structures represented by formula (2) may or may not be continuous, and the structures represented by formula (3) may be continuous. may not be consecutive.

Here, the meaning that R2 in formula (2) includes at least one of a glycidyl group and an epoxidized alkyl group among a hydrogen atom, an alkyl group, a glycidyl group and an epoxidized alkyl group. Supplementary explanation will be given. As a premise, there is one R2 in one structure represented by formula (2). The case where the acrylic resin has only one structure represented by formula (2) and the case where it has two or more structures will be described separately.

When the acrylic resin has one structure represented by formula (2), R2 is a glycidyl group or an epoxidized alkyl group.

When the acrylic resin has two or more structures represented by formula (2), at least one R2 in the structure represented by formula (2) is a glycidyl group or an epoxidized alkyl group, and the remaining R2 in the structure represented by formula (2) is a hydrogen atom or an alkyl group. Since R2 in at least one structure represented by formula (2) is a glycidyl group or an epoxidized alkyl group, R2 in all the structures represented by formula (2) is a glycidyl group or an epoxidized or an alkyl group.

The structure represented by formula (3) has a phenyl group (--Ph), --COOCH ₂ Ph, and --COO(CH ₂ ) ₂ Ph. Since —Ph, —COOCH ₂ Ph, and —COO(CH ₂ ) ₂ Ph are thermally stable, the strength of the cured prepreg is increased. Therefore, the moisture absorption and heat resistance of the metal-clad laminate 2 and the printed wiring board 3 (hereinafter collectively referred to as "substrate" in some cases) manufactured using prepreg as a material can be improved.

The acrylic resin preferably does not have unsaturated bonds such as double bonds and triple bonds between adjacent carbon atoms. That is, it is preferable that the adjacent carbon atoms of the acrylic resin are bound by a saturated bond (single bond). As a result, oxidation over time can be reduced, so that loss of elasticity and brittleness can be suppressed.

The weight average molecular weight (Mw) of the acrylic resin is preferably in the range of 200,000 or more and 850,000 or less. When the weight average molecular weight of the acrylic resin is 200,000 or more, the chemical resistance of the cured product can be improved. When the weight average molecular weight of the acrylic resin is 850,000 or less, the moldability of the thermosetting resin composition can be improved.

When the acrylic resin is contained in the thermosetting resin composition, the cured product of the prepreg becomes less likely to absorb moisture, thereby increasing the moisture resistance of the substrate and improving the insulation reliability. Moreover, even if the cured product of the prepreg absorbs moisture, the resistance to moisture absorption and heat of the substrate can be improved because the breaking strength of the resin constituting this cured product is increased.

Acrylic resin is a prepolymer having at least one or more epoxy groups in one molecule. Epoxy groups are one type of functional groups possessed by acrylic resins. The epoxy equivalent of the acrylic resin is preferably in the range of 1250 g/eq to 100000 g/eq, more preferably in the range of 2500 g/eq to 7000 g/eq. The epoxy equivalent in this case means the mass of the acrylic resin containing one equivalent of epoxy groups. If the epoxy equivalent is small, the concentration of epoxy groups is high, and if the epoxy equivalent is large, the concentration of epoxy groups is low.

The content of the acrylic resin is preferably in the range of 10 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the thermosetting resin. When the content of the acrylic resin is 10 parts by mass or more, the adhesion of the cured product to metal can be improved. The hardened|cured material can be made hard to burn because content of an acrylic resin is 30 mass parts or less.

A core-shell rubber and an acrylic resin may be used in combination, or only the core-shell rubber may be used. In such a case, the ratio of the core-shell rubber is preferably in the range of 50% by mass or more and 100% by mass or less with respect to the total mass of the core-shell rubber and the acrylic resin. Such optimal amounts provide the benefits of each of the core-shell rubber and the acrylic resin. That is, it is possible to improve the impact resistance, thermal shock resistance, laser workability, drill workability, and adhesion to metal of the cured product.

Next, the additive-type flame retardant will be explained. Specific examples of additive flame retardants include phosphate ester compounds, phosphazene compounds and antimony oxide. By containing the additive flame retardant in the thermosetting resin composition, the flame resistance of the cured product can be improved.

The additive flame retardant is preferably an additive phosphorus flame retardant. A halogen-free thermosetting resin composition can be obtained by using an additive-type phosphorus-based flame retardant instead of halogen. Specific examples of additive-type phosphorus-based flame retardants include phosphate ester compounds, phosphazene compounds, phosphite ester compounds, phosphine compounds, phosphinate compounds, polyphosphate compounds, phosphonium salt compounds and phosphine oxide compounds.

Next, the curing accelerator will be explained. The curing accelerator is appropriately selected according to the thermosetting resin and curing agent. A specific example of the curing accelerator is 2-ethyl-4-methylimidazole.

Next, optional components that are preferably not contained in the thermosetting resin composition will be described.

The thermosetting resin composition preferably contains substantially no pigments or dyes. Although some pigments and dyes can absorb ultraviolet rays, if at least one of the pigments and dyes is substantially contained in the thermosetting resin composition, the following problems may occur.

In general, pigments and dyes cannot form a crosslinked structure because they do not have crosslink points that can react with thermosetting resins. Therefore, if the cured product 51 contains an excessive amount of pigment and dye, the heat resistance of the cured product 51 may decrease.

Also, if the dispersibility of the pigment in the solvent is poor, the cured product 51 may not be uniformly colored. That is, the pigment locally agglomerates on the surface of the cured product 51, and the local agglomeration causes uneven coloring, resulting in non-uniform coloring.

Moreover, if the solubility of the dye in the solvent is poor, the cured product 51 may not be uniformly colored. That is, the dye locally precipitates on the surface of the cured product 51, and this local precipitation causes unevenness in coloration, resulting in non-uniform coloring.

Further, as the density of the conductor wirings 81 of the printed wiring board 3 progresses, there is a possibility that insulation failure may occur between the adjacent conductor wirings 81 . As a cause of this insulation failure, for example, a conductive pigment such as carbon black exists between the adjacent conductor wirings 81 in an agglomerated state, which causes a short circuit between the conductor wirings 81 . mentioned.

In contrast, in the present embodiment, when the thermosetting resin composition is cured, the first curing agent that absorbs ultraviolet rays forms a crosslinked structure and does not exist in isolation in the cured product. Problems like this are unlikely to occur. The thermosetting resin composition may contain at least one of a pigment and a dye as long as the ultraviolet shielding effect is not impaired.

Moreover, it is preferable that the thermosetting resin composition does not substantially contain halogen. Since the thermosetting resin composition is halogen-free, generation of dioxins can be suppressed when a printed wiring board or the like containing the cured product is incinerated. When flame resistance is to be imparted to the cured product, the thermosetting resin composition may contain a phosphorus-containing flame retardant instead of the halogen as described above. The thermosetting resin composition may contain a small amount of halogen as long as the ultraviolet shielding effect is not impaired and the generation of dioxins can be suppressed.

(2.2) Prepreg A prepreg 1 according to the present embodiment is shown in FIG. The prepreg 1 is sheet-like or film-like as a whole. The prepreg 1 is used as a material for the metal-clad laminate 2, a material for the printed wiring board 3, multilayering of the printed wiring board 3 (build-up method), and the like.

The prepreg 1 includes a base material 4 and a semi-cured material 50 of a thermosetting resin composition impregnated in the base material 4 .

Specific examples of the base material 4 include woven fabrics and non-woven fabrics. A specific example of the woven fabric is glass cloth. A specific example of the nonwoven fabric is glass nonwoven fabric. The glass cloth and the glass non-woven fabric are made of glass fibers, but may be made of reinforcing fibers other than glass fibers. Specific examples of reinforcing fibers include aromatic polyamide fibers, liquid crystal polyester fibers, poly(paraphenylenebenzobisoxazole) (PBO) fibers, and polyphenylene sulfide (PPS) resin fibers.

One sheet of prepreg 1 includes at least one sheet of base material 4 .

The semi-cured material 50 is a thermosetting resin composition in a semi-cured state. Here, the semi-cured state means the intermediate stage (B stage) of the curing reaction. The intermediate stage is the stage between the varnish state stage (A stage) and the cured state stage (C stage). When the prepreg 1 is heated, it melts once and then completely hardens into a hardened state. The cured prepreg 1 can form the insulating layer of the substrate.

The prepreg 1 preferably has a thickness of 100 μm or less, more preferably 60 μm or less, and even more preferably 40 μm or less. As a result, the thickness of the insulating layer can be reduced, and the thickness of the substrate can be reduced. The thickness of the prepreg 1 is preferably 10 μm or more.

(2.3) Metal-clad laminate A metal-clad laminate 2 according to this embodiment is shown in FIG. The metal-clad laminate 2 includes an insulating layer 52 and a metal layer 80 . The metal-clad laminate 2 is used as a material for the printed wiring board 3 and the like.

The insulating layer 52 is formed of the cured product 51 of the prepreg 1 . Although the insulating layer 52 has one substrate 4 in FIG. 2 , it may have two or more substrates 4 . The thickness of the insulating layer 52 is not particularly limited. A thick insulating layer 52 is effective for UV shielding, and a thin insulating layer 52 is effective for thinning the substrate. In order to achieve both of these, the thickness of the insulating layer 52 is preferably 100 μm or less, more preferably 60 μm or less, and even more preferably 40 μm or less. The UV shielding property largely depends on the first curing agent, but it is also effective to ensure the thickness of the insulating layer 52 to some extent. is more preferable.

The metal layer 80 is formed on one side or both sides of the insulating layer 52 . A specific example of the metal layer 80 is a copper layer. Although the metal layer 80 is formed on both sides of the insulating layer 52 in FIG. 2, the metal layer 80 may be formed on only one side of the insulating layer 52 . The metal-clad laminate 2 in which the metal layers 80 are formed on both sides of the insulating layer 52 is a double-sided metal-clad laminate. The metal-clad laminate 2 in which the metal layer 80 is formed only on one side of the insulating layer 52 is a single-sided metal-clad laminate.

(2.4) Printed Wiring Board FIG. 3 shows a printed wiring board 3 according to this embodiment. The printed wiring board 3 includes an insulating layer 52 and conductor wiring 81 . As used herein, the term "printed wiring board" means a board in which electronic components are not soldered and only wiring is present.

The insulating layer 52 is formed of the cured product 51 of the prepreg 1 . The insulating layer 52 is the same as the insulating layer 52 of the metal-clad laminate 2 described above.

The conductor wiring 81 is formed on one side or both sides of the insulating layer 52 . Although the conductor wiring 81 is formed on both sides of the insulating layer 52 in FIG. 3 , the conductor wiring 81 may be formed on one side of the insulating layer 52 .

Next, a method for manufacturing the printed wiring board 3 will be described. Specifically, it is a method of processing the metal-clad laminate 2 shown in FIG. 2 into the printed wiring board 3 shown in FIG. The printed wiring board 3 can be manufactured by removing unnecessary portions of the metal layer 80 of the metal-clad laminate 2 . The necessary portion remaining after removing the unnecessary portion of the metal layer 80 becomes the conductor wiring 81 .

First, as shown in FIG. 4A, a first etching resist 61 is applied or adhered to one metal layer 80 of the metal-clad laminate 2 and a second etching resist 62 is applied or adhered to the other metal layer 80 . Although the case where the first etching resist 61 and the second etching resist 62 are negative resists will be described below, they may be positive resists.

Next, as shown in FIG. 4B, a first photomask 601 is overlaid on the first etching resist 61 and a second photomask 602 is overlaid on the second etching resist 62 .

Here, the first photomask 601 has a light-transmitting portion 601a and a light-shielding portion 601b. The second photomask 602 has a light transmitting portion 602a and a light shielding portion 602b.

Then, double-sided exposure is performed. That is, each of the first photomask 601 and the second photomask 602 is irradiated with ultraviolet rays UV.

In the first photomask 601, the ultraviolet rays UV pass through the translucent portion 601a and are blocked by the light shielding portion 601b. A portion of the first etching resist 61 that is irradiated with ultraviolet rays UV through the transparent portion 601a is cured by photopolymerization to become the first resist layer 61a.

In this case, even if the ultraviolet rays UV pass through the first etching resist 61 , since the metal layer 80 exists beyond the first etching resist 61 , the ultraviolet rays UV are reflected by the metal layer 80 . Therefore, the problem of so-called backburning does not occur.

On the other hand, in the second photomask 602, the ultraviolet rays UV pass through the translucent portion 602a and are blocked by the light shielding portion 602b. A portion of the second etching resist 62 that is irradiated with the ultraviolet rays UV through the transparent portion 602a is cured by photopolymerization to form the second resist layer 62a.

In this case as well, even if the ultraviolet rays UV pass through the second etching resist 62 , since the metal layer 80 exists beyond the second etching resist 62 , the ultraviolet rays UV are reflected by the metal layer 80 . Therefore, the problem of so-called backburning does not occur.

Next, as shown in FIG. 4C, portions of the first etching resist 61 and the second etching resist 62 that have not been irradiated with the ultraviolet UV are removed with a developer. At this time, the first resist layer 61a and the second resist layer 62a remain without being dissolved in the developer. Portions other than the first resist layer 61a and the second resist layer 62a are dissolved in a developer and removed.

Next, as shown in FIG. 4D, portions of the metal layer 80 that are not protected by the first resist layer 61a and the second resist layer 62a are removed with an etchant.

After that, the first resist layer 61a and the second resist layer 62a are removed with a remover. Then, the printed wiring board 3 shown in FIG. 3 is obtained.

(2.5) Covered Printed Wiring Board A method for manufacturing the covered printed wiring board 30 will be described. Specifically, it is a method of processing the printed wiring board 3 shown in FIG. 3 into the coated printed wiring board 30 shown in FIG. 5C.

First, as shown in FIG. 5A, a first solder resist 71 is applied or adhered to one surface of the printed wiring board 3, and a second solder resist 72 is applied or adhered to the other surface. Although the case where the first solder resist 71 and the second solder resist 72 are negative resists will be described below, they may be positive resists.

Next, as shown in FIG. 5B, a first photomask 701 is overlaid on the first solder resist 71 and a second photomask 702 is overlaid on the second solder resist 72 .

Here, the first photomask 701 has a light-transmitting portion 701a and a light-shielding portion 701b. The second photomask 702 has a light transmitting portion 702a and a light shielding portion 702b.

Then, double-sided exposure is performed. That is, each of the first photomask 701 and the second photomask 702 is irradiated with ultraviolet rays UV.

In the first photomask 701, the ultraviolet rays UV pass through the translucent portion 701a and are blocked by the light shielding portion 701b. A portion of the first solder resist 71 that is irradiated with the ultraviolet rays UV through the transparent portion 701a is cured by photopolymerization to become the first resist layer 71a.

Here, even if the ultraviolet rays UV pass through the first solder-resist 71 at the place where the conductor wiring 81 exists between the first solder-resist 71 and the insulating layer 52, the conductor wiring 81 exists ahead of it. , the ultraviolet rays UV are reflected by this conductor wiring 81 .

On the other hand, in a portion where the conductor wiring 81 does not exist between the first solder resist 71 and the insulating layer 52 , the ultraviolet rays UV pass through the first solder resist 71 and irradiate the insulating layer 52 . In this case, since the insulating layer 52 is formed of the cured product 51 of the prepreg 1, it has a high ultraviolet shielding property. Therefore, even if ultraviolet rays UV pass through the transparent portion 701 a of the first photomask 701 and further through the first solder resist 71 , the ultraviolet rays UV are blocked by the insulating layer 52 . Therefore, it is possible to prevent the second solder resist 72 on the opposite side from being exposed to light through the insulating layer 52 . In other words, so-called back burn can be suppressed.

On the other hand, in the second photomask 702, the ultraviolet rays UV pass through the translucent portion 702a and are blocked by the light shielding portion 702b. A portion of the second solder resist 72 that is irradiated with the ultraviolet rays UV through the transparent portion 702a is cured by photopolymerization and becomes the second resist layer 72a.

Here, even if the ultraviolet rays UV pass through the second solder-resist 72 at the place where the conductor wiring 81 exists between the second solder-resist 72 and the insulating layer 52, the conductor wiring 81 exists ahead of it. , the ultraviolet rays UV are reflected by this conductor wiring 81 .

On the other hand, in places where the conductor wiring 81 does not exist between the second solder resist 72 and the insulating layer 52 , the ultraviolet rays UV pass through the second solder resist 72 and irradiate the insulating layer 52 . In this case as well, since the insulating layer 52 is formed of the cured product 51 of the prepreg 1, it has a high ultraviolet shielding property. Therefore, even if ultraviolet rays UV pass through the light-transmitting portions 702 a of the second photomask 702 and further through the second solder resist 72 , the ultraviolet rays UV are blocked by the insulating layer 52 . Therefore, it is possible to prevent the first solder resist 71 on the opposite side from being exposed to light through the insulating layer 52 . In other words, so-called back burn can be suppressed.

Next, as shown in FIG. 5C, portions of the first solder resist 71 and the second solder resist 72 that have not been irradiated with ultraviolet rays UV are removed with a developer. At this time, the first resist layer 71a and the second resist layer 72a remain without being dissolved in the developer. Portions other than the first resist layer 71a and the second resist layer 72a are dissolved in a developer and removed.

Covered printed wiring board 30 is obtained as described above. A portion of the conductor wiring 81 that is not protected by the first resist layer 71a and the second resist layer 72a can serve as a pad 81a. Electronic components (not shown) can be soldered to the pads 81a.

The printed circuit board has electronic components soldered to the pads 81a of the coated printed wiring board 30, and operates as an electronic circuit. Further, a semiconductor package is a printed circuit board in which electronic components are encapsulated.

(2.6) Resin-coated film A resin-coated film 10 according to this embodiment is shown in FIG. 6A. The resin-coated film 10 has a film shape or a sheet shape as a whole. A resin-coated film 10 includes a resin layer 11 and a support film 12 . The resin-coated film 10 is used for multilayering the printed wiring board 3 (build-up method).

The resin layer 11 is formed of a semi-cured material 50 of a thermosetting resin composition. The semi-cured material 50 can become a cured material 51 having high ultraviolet shielding properties by being heated. The resin layer 11 can thus form the insulating layer 52 .

The resin layer 11 preferably has a thickness of 100 μm or less, more preferably 60 μm or less, and even more preferably 40 μm or less. As a result, the thickness of the insulating layer 52 can be reduced, and the thickness of the substrate can be reduced. It is preferable that the thickness of the resin layer 11 is 10 μm or more.

The support film 12 supports the resin layer 11 . Such support makes it easier to handle the semi-cured resin layer 11 . The support film 12 is, for example, an electrically insulating film. Specific examples of the support film 12 include polyethylene terephthalate (PET) film, polyimide film, polyester film, polyparabanic acid film, polyetheretherketone film, polyphenylene sulfide film, aramid film, polycarbonate film, and polyarylate film. The support film 12 is not limited to these films. A release agent layer (not shown) may be provided on the surface of the support film 12 that supports the resin layer 11 . The release agent layer allows the support film 12 to be peeled off from the resin layer 11 as necessary. Preferably, the support film 12 is removed from the insulating layer 52 after forming the insulating layer 52 .

Although one surface of the resin layer 11 is covered with the support film 12 in FIG. 6A, the other surface of the resin layer 11 may be covered with the protective film 13 as shown in FIG. 6B. By coating both sides of the resin layer 11 in this manner, the semi-cured resin layer 11 can be handled more easily. In addition, it is possible to prevent foreign substances from adhering to the resin layer 11 . The protective film 13 is, for example, an electrically insulating film. Specific examples of the protective film 13 include polyethylene terephthalate (PET) film, polyolefin film, polyester film, polymethylpentene film, and the like. Protective film 13 is not limited to these films. A release agent layer (not shown) may be provided on the surface of the protective film 13 that is overlaid on the resin layer 11 . The release agent layer allows the protective film 13 to be peeled off from the resin layer 11 as necessary.

(2.7) Resin-coated Metal Foil FIG. 7 shows a resin-coated metal foil 100 according to this embodiment. The resin-coated metal foil 100 has a film shape or a sheet shape as a whole. A resin-coated metal foil 100 includes a resin layer 101 and a metal foil 102 . The resin-coated metal foil 100 is used for multilayering the printed wiring board 3 (build-up method).

The resin layer 101 is formed of a semi-cured material 50 of a thermosetting resin composition. The semi-cured material 50 can become a cured material 51 having high ultraviolet shielding properties by being heated. The resin layer 101 can thus form the insulating layer 52 .

The resin layer 101 preferably has a thickness of 100 μm or less, more preferably 60 μm or less, and even more preferably 40 μm or less. As a result, the thickness of the insulating layer 52 can be reduced, and the thickness of the substrate can be reduced. It is preferable that the thickness of the resin layer 101 is 10 μm or more.

A resin layer 101 is adhered to the metal foil 102 . A specific example of the metal foil 102 is copper foil. The metal foil 102 can form the conductor wiring 81 by removing unnecessary portions by etching.

(3) Summary As described above, the thermosetting resin composition according to the first aspect is a thermosetting resin composition containing a thermosetting resin and an inorganic filler. A thermosetting resin contains a curing agent. The Gardner color number of a 3% by mass methyl ethyl ketone solution of the curing agent is 15 or more. The content of the curing agent is 10% by mass or more with respect to the total solid content of the thermosetting resin composition.

According to the first aspect, it is possible to obtain a cured product (51) having high ultraviolet shielding properties.

A thermosetting resin composition according to a second aspect, in the first aspect, contains a naphthalene-type phenolic resin as the curing agent.

According to the second aspect, it becomes easier to absorb ultraviolet rays than a novolak-type phenolic resin.

In the first or second aspect, the thermosetting resin composition according to the third aspect has an inorganic filler content of 200 parts by mass or less with respect to 100 parts by mass of the thermosetting resin.

According to the third aspect, the moldability of the thermosetting resin composition can be improved. Furthermore, generation of voids in the cured product (51) can be suppressed.

In a thermosetting resin composition according to a fourth aspect, in any one of the first to third aspects, the thermosetting resin further contains a reactive flame retardant.

According to the fourth aspect, the flame resistance of the cured product (51) can be improved.

A thermosetting resin composition according to a fifth aspect, in any one of the first to fourth aspects, further contains core-shell rubber, acrylic resin, or both core-shell rubber and acrylic resin.

According to the fifth aspect, it is possible to improve at least one of the impact resistance, thermal shock resistance, laser processability, drilling processability, and adhesion to metal of the cured product.

A thermosetting resin composition according to a sixth aspect, in any one of the first to fifth aspects, further contains an additive flame retardant.

According to the sixth aspect, the flame resistance of the cured product (51) can be further improved.

A prepreg (1) according to a seventh aspect comprises a substrate (4) and a semi-cured product (50) of any one of the first to sixth thermosetting resin compositions impregnated in the substrate (4). , is equipped with

According to the seventh aspect, it is possible to obtain a cured product (51) having high ultraviolet shielding properties.

The prepreg (1) according to the eighth aspect has a thickness of 100 μm or less in the seventh aspect.

According to the eighth aspect, it is possible to obtain a cured product (51) having a thickness of 100 μm or less and having high UV shielding properties.

A metal-clad laminate (2) according to a ninth aspect comprises an insulating layer (52) formed of the cured product (51) of the prepreg (1) of the seventh or eighth aspect, and one side of the insulating layer (52) or a metal layer (80) formed on both sides.

According to the ninth aspect, it is possible to enhance the ultraviolet shielding property of the insulating layer (52).

A printed wiring board (3) according to a tenth aspect comprises an insulating layer (52) formed of the cured product (51) of the prepreg (1) of the seventh or eighth aspect, and one side or and conductor wiring (81) formed on both sides.

According to the tenth aspect, it is possible to enhance the ultraviolet shielding property of the insulating layer (52).

A resin-coated film (10) according to an eleventh aspect comprises a resin layer (11) formed of a semi-cured product (50) of any one of the first to sixth thermosetting resin compositions, and a resin layer (11 ), and a support film (12) for supporting ).

According to the eleventh aspect, it is possible to obtain a cured product (51) having high ultraviolet shielding properties.

A resin-coated metal foil (100) according to a twelfth aspect comprises a resin layer (101) formed of a semi-cured product (50) of any one of the first to sixth thermosetting resin compositions, and a resin layer ( 101) is attached to a metal foil (102).

According to the twelfth aspect, it is possible to obtain a cured product (51) having high ultraviolet shielding properties.

EXAMPLES The present disclosure will be specifically described below with reference to examples.

[Examples 1 to 13 and Comparative Examples 1 to 5]
[Thermosetting resin composition]
The following materials were prepared as raw materials for the thermosetting resin composition.

(Thermosetting resin)
・ Triphenylmethane type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name “EPPN-502H”, epoxy equivalent: 158 to 178 g / eq)
・ Naphthalene type epoxy resin (manufactured by DIC Corporation, trade name “HP-9900”, epoxy equivalent: 272 g / eq)
・ Naphthalene type epoxy resin (manufactured by DIC Corporation, trade name “HP-4710”, epoxy equivalent: 170 g / eq)
・ Bismaleimide resin (manufactured by Nippon Kayaku Co., Ltd., trade name “MIR-3000”, manufactured by Nippon Kayaku Co., Ltd.)
(Curing agent: first curing agent)
A naphthalene-type phenolic resin represented by formula (E) was placed in a non-sealed container, and the inside of this container was stirred in the presence of air. By adjusting the oxidation treatment temperature in the range of 50 ° C. or higher and 100 ° C. or lower and adjusting the oxidation treatment time in the range of 6 hours or higher and 72 hours or lower, the following two types of oxidized naphthalene-type phenol resins are obtained. got

- Oxidized naphthalene-type phenolic resin (hydroxyl equivalent: 153 g/eq, Gardner color number 18)
- Oxidized naphthalene-type phenolic resin (hydroxyl equivalent: 153 g/eq, Gardner color number 15)
(Curing agent: second curing agent)
・ Novolac phenol resin (manufactured by DIC Corporation, trade name “TD-2090”, hydroxyl equivalent: 105 g / eq, Gardner color number 1 or less)
- Naphthalene-type phenol resin (manufactured by DIC Corporation, product name "HPC-9500", hydroxyl equivalent: 153 g / eq, Gardner color number 7)
The Gardner color number of the curing agent was determined according to JIS K 0071-2 using a 3 mass % methyl ethyl ketone solution as a sample.

(Reactive flame retardant)
・ Reactive phosphorus-based flame retardant (phosphorus-modified phenolic resin, manufactured by Dow Chemical, trade name “XZ-92741”, hydroxyl equivalent: 550 g / eq)
・ Reactive phosphorus-based flame retardant (phosphorus-modified phenolic resin, manufactured by DIC Corporation, trade name “HPC-9080”, hydroxyl equivalent: 373 g / eq)
(Inorganic filler)
・ Fused silica (manufactured by Admatechs Co., Ltd., trade name “SC-2500SEJ”, average particle size: 0.5 μm)
・ Aluminum hydroxide (manufactured by Sumitomo Chemical Co., Ltd., trade name “C-301N”, average particle size: 1.5 μm)
・ Aluminum hydroxide (manufactured by Sumitomo Chemical Co., Ltd., trade name “CL-303”, average particle size: 4 μm)
(core shell rubber)
・Core shell rubber (manufactured by Mitsubishi Chemical Corporation, trade name “SRK200A”, core: silicone/acrylic copolymer, shell: acrylonitrile/styrene, average particle size: 0.15 μm)
・Core shell rubber (manufactured by Aica Kogyo Co., Ltd., product name “AC3816N”, core: crosslinked acrylic polymer, shell: polymethyl methacrylate, average particle size: 0.5 μm)
・Core shell rubber (manufactured by Aica Kogyo Co., Ltd., product name “AC3364”, core: crosslinked acrylic polymer, shell: polymethyl methacrylate, average particle size: 0.1 μm)
(acrylic resin)
・ Acrylic resin (manufactured by Nagase ChemteX Co., Ltd., product name “SG-P3 Kai 197”, weight average molecular weight 700,000)
(dye)
・ Oil-soluble dye (manufactured by Chuo Synthetic Chemical Co., Ltd., trade name “Oil Red 168”)
(Curing accelerator)
・ 2-ethyl-4-methylimidazole (manufactured by Shikoku Chemical Industry Co., Ltd., trade name “2E4MZ”)
(Thermosetting resin composition)
A thermosetting resin, a curing agent, an inorganic filler, a phosphorus-containing flame retardant, a core-shell rubber, an acrylic resin, and a curing accelerator are blended in the proportions shown in Table 1, and then mixed with a solvent so that the solid content concentration is 65% by mass. A thermosetting resin composition was prepared by diluting, stirring, mixing and homogenizing. As the above solvent, a mixed solvent of toluene and methyl ethyl ketone (volume ratio 1:10) was used in Example 8, and only methyl ethyl ketone was used in other examples and comparative examples.

(prepreg)
A glass cloth (#1017 type, E glass manufactured by Nitto Boseki Co., Ltd.) was impregnated with the thermosetting resin composition so that the cured prepreg had a thickness of 25 μm. The thermosetting resin composition with which the glass cloth was impregnated was heated and dried by a non-contact type heating unit until it reached a semi-cured state. The heating temperature was 130-140°C. As a result, the solvent in the thermosetting resin composition was removed, and a prepreg comprising a glass cloth and a semi-cured product of the thermosetting resin composition impregnated in the glass cloth was produced. The resin content (resin amount) of the prepreg was within the range of 68% by mass or more and 74% by mass or less with respect to the entire prepreg (100% by mass).

(Metal clad laminate)
Ultra-thin copper foil with carrier foil (thickness of carrier foil: 18 μm, thickness of ultra-thin copper foil: 2 μm) is superimposed on both sides of one prepreg, and heat-pressed to form A first double-sided metal-clad laminate having an insulating layer with a thickness of 25 μm was produced. The conditions for hot-press molding are 210° C., 4 MPa, and 120 minutes.

A second double-sided metal-clad laminate having an insulating layer with a thickness of 25 μm was manufactured by laminating copper foil (thickness: 12 μm) on both surfaces of one prepreg and heat-pressing the laminate. The conditions for hot-press molding are 210° C., 4 MPa, and 120 minutes.

[Characteristic evaluation]
The ultra-thin copper foils on both sides of the first double-sided metal-clad laminate were removed by etching to obtain only the insulating layer. Using this insulating layer as a sample, evaluations of ultraviolet shielding properties, moldability, heat resistance 1 and flame resistance were carried out.

Flame resistance 2 was evaluated using the second double-sided metal-clad laminate as a sample without removing the copper foils on both sides.

<Ultraviolet shielding rate>
Exposing machine (manufactured by Hitech Co., Ltd., model number "HTE-3000M") and ultraviolet illuminance meter (manufactured by Oak Manufacturing Co., Ltd., model number "UV-M02", receiver "UV-42" (peak wavelength 400 nm)) between the sample was interposed, and the transmittance of ultraviolet rays emitted from the exposing device through the sample and irradiated onto the photodetector was measured with an ultraviolet illuminometer. Then, the ultraviolet shielding rate (%) was calculated according to the following formula.

UV shielding rate (%) = 100 - transmittance <Moldability>
The surface of the sample was visually observed to confirm the presence or absence of scratches, and the cross section of the sample was observed under a microscope to confirm the presence or absence of voids. The sample size is 410 mm×510 mm×25 μm thick. Moldability was determined according to the following criteria.

A: No faintness or voids B: At least any faintness or voids present in a region (peripheral region) within 10 mm from the outer peripheral edge of the sample C: At least any faintness or voids present in the outer peripheral region (Central region), or present in both the central region and the peripheral region.

<Heat resistance 1>
The Tg of the sample was measured using a dynamic viscoelasticity measuring device (manufactured by SII Nanotechnology Co., Ltd., model: DMS6100). Tg was taken as the temperature at which tan δ is maximum in the chart showing the relationship between the loss tangent (tan δ) obtained during the heating process of the dynamic viscoelasticity test and the temperature. The sample size is 5 mm×50 mm×25 μm thick. The measurement conditions were deformation mode: tension, frequency: 10 Hz, and temperature increase rate: 5°C/min.

<Heat resistance 2>
The heat resistance of the second double-sided metal-clad laminate was evaluated based on JIS C6481 using a small high-temperature chamber (manufactured by Espec Co., Ltd., model: STH-120). Specifically, the second double-sided metal-clad laminate was allowed to stand in the small high-temperature chamber set at 270° C. for 1 hour, and then taken out to confirm the presence or absence of blistering (delamination) of the copper foil. . The size of the sample is 50 mm×50 mm×49 μm thick (25 μm thick insulating layer, 12 μm thick copper foil on both sides of the insulating layer).

<Flame resistance>
The flame resistance of the sample was confirmed according to the evaluation test method according to UL94 (combustibility test of plastic materials) of UL standard (Underwriters Laboratories Inc.).

REFERENCE SIGNS LIST 1 prepreg 2 metal-clad laminate 3 printed wiring board 4 base material 50 semi-cured product 51 cured product 52 insulating layer 80 metal layer 81 conductor wiring

Claims (11)

A thermosetting resin composition containing a thermosetting resin and an inorganic filler,
The thermosetting resin includes at least one of an epoxy resin and a bismaleimide resin, and a curing agent,
The curing agent contains an oxidized naphthalene-type phenolic resin,
The oxidized naphthalene-type phenol resin contains at least one skeleton of a 1,4-naphthoquinone skeleton represented by formula (F) and a 1,2-naphthoquinone skeleton represented by formula (G). ,
The Gardner color number of a 3% by mass methyl ethyl ketone solution of the curing agent is 15 or more,
The content of the curing agent is 10% by mass or more with respect to the total solid content of the thermosetting resin composition,
The inorganic filler contains at least one of silica and aluminum hydroxide,
A thermosetting resin composition.

In Formula (F) and Formula (G), each of R6 and R7 is a hydrogen atom, a methyl group, an ethyl group (--CH ₂ CH ₃ ) or a methoxy group. Substituents other than R6 and R7 are hydrogen atoms . The content of the inorganic filler is 200 parts by mass or less with respect to 100 parts by mass of the thermosetting resin.
The thermosetting resin composition according to claim 1. The thermosetting resin further contains a reactive flame retardant,
The thermosetting resin composition according to claim 1 or 2. Further containing core-shell rubber, acrylic resin, or both core-shell rubber and acrylic resin,
The thermosetting resin composition according to any one of claims 1 to 3. Further containing an additive flame retardant,
The thermosetting resin composition according to any one of claims 1 to 4. a substrate;
A semi-cured product of the thermosetting resin composition according to any one of claims 1 to 5 impregnated in the base material,
prepreg. thickness is 100 μm or less,
The prepreg according to claim 6. an insulating layer formed of the cured prepreg according to claim 6 or 7;
a metal layer formed on one or both sides of the insulating layer;
Metal clad laminate. an insulating layer formed of the cured prepreg according to claim 6 or 7;
and conductor wiring formed on one side or both sides of the insulating layer,
printed wiring board. A resin layer formed of a semi-cured product of the thermosetting resin composition according to any one of claims 1 to 5, and a support film that supports the resin layer,
Film with resin. A resin layer formed of a semi-cured product of the thermosetting resin composition according to any one of claims 1 to 5, and a metal foil to which the resin layer is bonded,
Metal foil with resin.

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